1. Field of the Invention
The invention generally relates to alarm notification within telecommunication systems, and more particularly, to alarm notification for power out linear amplifiers (POLNA) in base transceiver stations.
2. Background of the Invention
In cellular communication systems, to increase the signal received from the mobile devices, tower mounted amplifiers are located within base transceiver stations. The tower mounted amplifiers increase the received signal by approximately 15 decibels (db); and, as a result of the increase in the received signal, the range of the base transceiver station is also increased.
The tower mounted amplifiers are powered from power out linear amplifiers, which also provide alarm indication for the tower mounted amplifiers. An electronic card in a power out linear amplifier provides a 15 volt output and includes a current sensing device that provides the alarm indication. When the current sensing device detects a current draw from the tower mounted amplifiers, which is above a predetermined threshold, it provides an alarm indication.
The current sensing device is designed to have an operating range of approximately 200–800 milliamps. When a tower mounted amplifier is operating normally it will maintain a current draw of approximately 200 milliamps and when it fails the current draw will be substantially higher, for example 1100 milliamps. The higher current draw triggers the alarm indication.
One of the problems with the current sensing devices is that they provide intermittent alarm indication. They do not always alarm upon tower amplifier failure. The current sensing device may not provide an alarm indication for failure conditions not associated with an increase in current draw. For example, when the electronic card in the power out linear amplifier fails, it does not provide the 15 volt output to the tower mounted amplifier. This condition does not provide any alarm indication; even though, the tower mounted amplifier is not operational. In many cases, the failure of the electronic card may be due to component failures caused by weather conditions, such as lightning.
Without the alarm indication from the current sensing device, the most likely method for detecting the failure is to conduct an analysis of the call processing performance of a base transceiver station. Then, because of a decreased number of processed calls, an investigation may be initiated and the non-operational tower mounted amplifier may be found.
When the electronic card in the power out linear amplifier fails and the tower mounted amplifier is not functioning properly, the signal received at the base transceiver station may be greatly degraded. For example, a two mile coverage radius around the base transceiver station may be reduced to a half or a quarter of a mile, when the electronic card in the power out linear amplifier fails and the tower mounted amplifier is not operating properly.
Therefore, to maintain an acceptable coverage radius for a base transceiver station, there is a need for a failure detection device for a power out linear amplifier, which provides a failure indication when the electronic card powering the tower mounted amplifier fails.